1. Field of the Invention
The present invention relates to a method of producing a semiconductor device and a configuration thereof. More particularly, it relates to a method of producing a resin-sealed semiconductor device and a configuration thereof which make it possible to decrease the size, thickness, weight and cost of the device.
2. Description of the Related Art
FIGS. 15A and 15B show a gull-wing type semiconductor device with the configuration of the prior art, FIG. 15A being a cross sectional view thereof and FIG. 15B being a top view thereof.
A semiconductor device of this configuration is generally produced in such steps as shown in FIG. 16, in a procedure described below. A semiconductor element 3 is bonded by means of a die bonding material 2 on an island 24 of a lead frame 6 which has the islands 24 and leads 1 as shown in FIG. 17. Then after connecting an inner lead section of the lead 1 surrounding the island 24 to an electrode pad located on the semiconductor element 3 by wire bonding using a wire 4 such as gold wire, the elements are sealed individually on both sides of the lead frame 6 by using a sealing resin 5. FIG. 18 is a top view of the semiconductor device with the configuration of the prior art after being sealed with resin. In a last stage, an outer lead section of the lead 1 is plated with tin or the like, cut off from the lead frame 6 and formed in gull wing shape, thereby to obtain the semiconductor device as shown in FIGS. 15A and 15B.
In the production method of the prior art, it is necessary to prepare the lead frame 6 having the islands 24 matched to the size of the semiconductor elements 3 and molding dies (not shown) for sealing the individual semiconductor elements with a resin. Therefore, when semiconductor elements 3 of different specifications are used, it is necessary to prepare different lead frames 6 and different molding dies for the various specifications.
In the semiconductor device of the prior art shown in FIGS. 15A and 15B, there has been a limitation on the reduction of the size and weight because the resin covers both sides of the lead frame 6.
Moreover, because heat generated by the semiconductor element 3 is dissipated through the lead 6, it is difficult to apply the device to high-output power transistors which generated much heat. Because of the relatively long connection between the semiconductor element 3 and a mother board, it is also difficult to apply the device to high-frequency transistors or the like.
To counter such problems as described above, a molded transistor having only one side of a lead being molded with a resin is disclosed, for example, in Japanese Patent Kokai Publication No. 62-134945. However, since production of such a molded transistor requires different lead frames for different specifications as in the prior art and molding with the resin is carried out individually for each semiconductor element, different molding dies must be prepared according to different specifications and therefore the above problems are not solved.
Also the devices are mounted on the mother board by using flat leads according to this prior art technology, but it cannot be applied to devices which generate much heat because of relatively small lead area.